Astronomical understanding, accurate calendars and knowledge of exact geographic latitudes and longitudes were essential for all Islamic cities and towns. This body of astronomical knowledge was not accumulated for abstract scientific advancement but mainly for religious obligations. Three of the Five Pillars of Islam require astronomically precise information: to determine accurate hours for the call to prayer, the time of sunrise and sunset for fasting during Ramadan, and for tracking the phases of the moon that marked the start of a new lunar month. The exact directions were necessary especially for the Hajj, the journey to Mecca for every able Muslim. The extended journeys through desert sands by long-stretching caravans that transported precious cloth, carpets and exotic spices also required
